Trend Analysis of the Average Temperature in Southern Half of Iran During the Recent Four Decades

Average temperature increase because of climate change is considered as an important environmental problem of human for which many studies have been conducted in the recent years. In this study, trends of the average air temperature of the Southern half of Iran in monthly and annual time scales were analyzed using the non-parametric Mann-Kendall method. Data used were the average air temperature data of 14 synoptic stations, covering the period of 1971-2010. The Sen's slope estimator was used for estimation of the slope of the trend line. Results showed that in annual time scale, 11 stations (79% of the selected stations) experienced a significant increasing trend and only two stations (Birjand and Chabahar) did not show significant positive trend in air temperature series. The Shahrekord station showed negative (insignificant) trend. The most strong positive trend slope in the case of annual temperature belonged to the Kerman station, which was equal to 0.061 °C /yr. In monthly time scale, the numbers of months having positive trends were 13 times greater than those with negative trends. Except the Birjand, Chabahar and Shahrekord stations which experienced both negative and positive trends, the other stations only showed a positive trend. February and November had the most (all of the stations) and less (7 stations) numbers of stations with significant positive trends, respectively.